There is known a hot-rolling device that produces a metal wire such as a bar steel wire from a slab such as a billet. This hot-rolling device is provided with, for example, a heating furnace, a roughing roller, a finishing roller, a pinch roll, and a coiling machine, and these are disposed and arranged in order from the upstream side. In this device, a slab is heated in the heating furnace and subjected to continuous rolling to become a wire, which is then wound in a coil form by the coiling machine. An oxide scale such as an oxide film adheres to the surface of the metal wire thus coiled. Here, the produced metal wire may be subjected to a drawing treatment using a drawing die for the purpose of improving the dimension accuracy and mechanical properties. In this case, it is necessary that a descaling process that removes the oxide scale is performed before the drawing treatment.
Generally, pickling is widely used for performing descaling on a metal wire. Pickling is a method of descaling by immersing the metal wire wound in a coil shape into an acid solution tank. It is assumed that various kinds of oxide scale can be efficiently removed by optimizing the type, concentration, and temperature of the acid (See, for example, Patent Literature 1).
Also, besides pickling, descaling of blasting type is known in which the metal wire in a coil form is paid out and drawn in a straight line shape to travel, and hard particles are allowed to collide at a high speed against the surface of the traveling metal wire, so as to perform descaling. As a representative example, there is known a shot blasting method that projects spherical particles onto the surface of a metal wire by centrifugal force of an impeller (See, for example, Patent Literature 2).
Meanwhile, as a device for polishing, Patent Literature 3 discloses a wet honing device that sprays a mixture (slurry), which is obtained by homogeneously mixing water and hard particles, onto a work piece with use of compressed air.
Descaling by pickling disclosed in Patent Literature 1 involves problems such as increased costs for discarding the consumed acid and contamination of the working environment by evaporation of the acid, and hence is not preferable. The shot blasting method disclosed in Patent Literature 2 raises problems such as being incapable of completely removing the oxide scale that adheres thinly to the base iron and inviting contamination of the working environment by crushed particles turned into powder dust.